<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    @media (min-width:375px) {
      :root {
        font-size: 1px;
      }
    }
    @media (min-width:414px) {
      :root {
        font-size: 2px;
      }
    }

    .box {
      width: 100rem;
      height: 100rem;
      background-color: orange;
    }
  </style>
</head>

<body>
  <div class="box"></div>
</body>

</html>